


Comparative Advantages

by Anonymous



Series: 100 starker fics [3]
Category: Iron Man (Movies), Marvel Cinematic Universe, Spider-Man (Tom Holland Movies), Spider-Man - All Media Types, The Avengers (Marvel Movies)
Genre: F/M, Genderswap, M/M, Seduction, Size Kink, Virginity Kink, Women's Underwear, nothing explicit in chapter one, temporary genderswap, women's clothes
Language: English
Status: In-Progress
Published: 2020-05-17
Updated: 2020-05-17
Packaged: 2021-03-02 22:13:42
Rating: Explicit
Warnings: Creator Chose Not To Use Archive Warnings, Underage
Chapters: 1
Words: 3,656
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/24234118
Author URL: https://archiveofourown.org/
Summary: A spell turns Peter into a girl. Peter notices Mr. Stark's behavior towards him has changed as a result, and decides to take advantage.
Relationships: Peter Parker/Tony Stark
Series: 100 starker fics [3]
Series URL: https://archiveofourown.org/series/1746880
Comments: 24
Kudos: 122
Collections: Anonymous





	Comparative Advantages

Peter probably shouldn't have noticed the change in Mr. Stark's behavior right away, what with the headache of accidentally getting turned into a girl, but he does. That probably says something about how focused on Mr. Stark he is, but right now he doesn't care how unhealthy and fruitless it is to be dizzy with love for a married man thirty years older than him, he cares that for the first time ever he might have a chance.

In this new body, Mr. Stark treats him differently. He used to clap Peter on the shoulder, give him go-get-them-tiger, one-armed hugs and there was the occasional jab with an elbow to get his attention. Peter was hyperaware of all of them and more exposure never really made Mr. Stark's touch any less electrifying, but it wasn't like it is now. Now, Mr. Stark guides Peter with a hand at the small of his back, low, just above the curve of his waist. Mr. Stark touches his arm above the elbow when asking a question he thinks might upset Peter and rests his palm there when he wants Peter to calm down. Mr. Stark tucks Peter's hair behind his ear when they're leaning over a schematic together without even slowing down their back and forth, like it's nothing.

These days, Peter's very good about rolling with the punches. He took so much in stride that the new body, the fact that it's been three months and the spell hasn't worn off no matter what Doctor Strange insisted, it's all just another background thing by now. Mr. Stark is still mad on his behalf (or at least Peter would like to think it's on his behalf and not because of Mr. Stark's competitive snark-off vibe with Doctor Strange) and Peter appreciates the fact that Mr. Stark's still trying to reverse it, but for himself he's already... resigned. Compared to Uncle Ben dying or turning to dust and then coming back to life, this is... not nothing, but tolerable. Peter can live with being a girl.

He can more than live with Mr. Stark treating him like a girl.

It should probably feel demeaning or something, except it really, really doesn't. Mr. Stark was protective of Peter to begin with, only now he's protective in a way that makes Peter feel cherished. As childish and embarrassing as that sounds even in Peter's head, it's still the truth.

Mr. Stark insists on training Peter himself so Peter will get used to his body's lower center of gravity and Peter gets drunk on his touches, all the little corrections of his stance and posture that have softened along with all of Mr. Stark's other touches until they feel almost like caresses.

Peter's so glad arousal is so much easier to hide as a girl.

At first, he doesn't do anything but bask in the light reflected from this silver lining. He tries not to worry Aunt May, to convince her he's okay and not irreparably psychologically damaged before she gets it into her head she's been a bad guardian again. He lets himself get carted to and from his new school by Happy - the swanky private equivalent to Midtown they couldn't afford and where the sudden transfer of one Petra Parker turned out to be less temporary than imagined. Somehow the news of who's footing the bill spread, and everyone seems to believe he's Tony Stark's secret love child.

At home, Peter brushes his teeth without meeting his eyes in the mirror and showers without looking down at himself. He dresses in the clothes Mr. Stark bought for him - jeans and hoodies and t-shirts with dumb nerdy slogans, only ones of a slightly different cut.

He hasn't touched himself since _it_ happened, but he's had a couple of wet dreams. They're indistinct and tame - big hands on Peter's waist, someone kissing him on the cheek with an open, bristly mouth before somehow there's friction and Peter feels good and then on the morning he feels relaxed so he must have come.

But slowly the idea that he could have more starts taking root. Mr. Stark likes women. Peter's never seen him act nearly so grabby or familiar with any women though. He assumed that Mr. Stark touched him so much before as a sort of mix of friendliness, assertion of authority and a substitute for actual communication. Not that Mr. Stark's playing any dominance games, no, he's just so used to having authority over the people he interacts with - and so averse to strangers, especially men, having any authority over him - that he makes friends by claiming people's space. Peter's seen him clap Thor on a biceps as thick as a tree-trunk like other people would have patted a pit bull on the neck, but it had no malice or dismissal behind it.

Peter figures he got slotted at the intersection between "kid I care about, touch like my dad touched me when he was trying to show approval" and "friend/teammate I trust, touch until we bond then touch some more". The girl stuff complicated the whole thing because Mr. Stark didn't _trust_ Black Widow and so his only recent framework for touching women he's close to has been in the context of dating.

Peter realizes all of this instinctually. Since the bite reading people's body language, when they're tensing to attack and so on, has become as natural as doing a somersault in the air. He knows Mr. Stark isn't nearly as aware though, especially about his own behavior. So Peter wonders whether he could get Mr. Stark to become even more touchy-feely.

It's nothing... inappropriate. Peter's conscience ought to be completely silent about this. Of course Mr. Stark's taken and Peter knows it's wrong to try and make a move, but this is nothing like that. It's not cheating, not even close to it, so it's okay. 

Peter starts by leaning closer to Mr. Stark, dragging his chair a little nearer. He lets his leg jiggle as much as it wants - Mr. Stark finds that distracting, and he gets between Mr. Stark and his cup of coffee or screwdriver. He can sense the right approach is not to touch Mr. Stark more himself, but to make Mr. Stark get even more used to reaching for Peter.

It works like a charm. Mr. Stark rests his arm on the back of Peter's chair, grabs Peter's nervous knee under the table while chastising him under his breath, reaches around Peter in another not-hug in his quest for caffeine.

All when they're alone, because Peter makes sure to keep a casual distance when Colonel Rhodes or Ms. Potts are around - and Peter is so irrationally glad it's still Ms. Potts and not Mrs. Stark. He feels happier and Mr. Stark seems more relaxed and nobody's hurt and there's no downside.

The next part isn't Peter's fault either. It's nobody's fault.

Ms. Potts invites Peter to the Stark holiday party. It's on the Friday before Christmas, so the 21st, which means it won't interfere with May and Peter's family plans. Peter's trying not to dwell on the fact that it also won't interfere with Mr. Stark and Ms. Potts's intimate couple celebration. Peter assumes that's a thing because there's no way anyone newly married to Mr. Stark wouldn't use their first New Year's together to remind him just why it was worth it to get hitched. Feeling jealous is no use whatsoever, so Peter tries not to be.

Instead, he asks whether the party's going to be anything like the NBA finals party because he doesn't want to show up if all he'll be able to do is ogle Mr. Stark on a screen. Ms. Potts misunderstands that Peter's talking about the dress code, so she very tactfully prompts Mr. Stark to offer to buy Peter fancy clothes of his choosing.

"It's actually a bribe because I need as many not-boring people there as possible for the sake of my sanity. You'll be doing me a favor," Mr. Stark says, gesturing expansively and catching Peter slightly on the shoulder before sticking his hand back in his pocket.

Peter can't do anything but nod silently, afraid his voice would come out way too breathy. Mr. Stark smiles at him and it's slow, thoughtful, as if he were seeing Peter for the first time.

He expects a delivery to May's door some day soon, or for Mr. Stark to throw him his credit card and say "don't spend it all on one place" or something.

Instead Peter gets called-in early from ballet practice by a teacher wearing the shell-shocked expression normal people tend to adopt after unexpectedly meeting Mr. Stark for the first time. Mr. Stark's here to pick Peter up.

Peter rushes through his shower and change to find Mr. Stark smoking a cigarette against the railing in front of the main entrance. He's wearing mirrored aviators, a light sweater and slacks for once, and he looks so sleek and untouchable Peter just about trips and barrels into him.

"Whoa, kid," says Mr. Stark, keeping Peter from falling over. Peter doesn't step back quickly enough and his nose almost sinks into Mr. Stark's collar so that he gets a whiff of Mr. Stark's cologne and the warm smell of his skin. It's the kind of smell that invites you to melt like a slab of butter in the sun and Peter nearly does before Mr. Stark casually pushes past him. "Didn't have to break a leg rushing here. Is your hair still wet? May will kill me if you get sick on my watch."

There's a quick ruffle through Peter's hair, presumably to check it for dampness, and it's like someone stuck a pin to Peter's not-quite-brand-new clit, only in a good way.

He trots after Mr. Stark to the car on rubbery legs, letting Happy stash his bag in the trunk instead of flinging it on the back seat next to him like he usually does. Now Mr. Stark's there and Peter doesn't want anything between them.

Mr. Stark smiles at Peter and stubs out the cigarette, and Peter finds his voice.

"What's with the cancer stick?"

Mr. Stark groans and throws his head back. Thankfully it sounds more petulant than pornographic.

"Don't you start too, kid. I could grow a dozen new sets of lungs right now with Helen Cho's tech, it's fine. I don't know why everyone's so determined not to allow me a single vice."

Peter wonders who that everyone is, before deciding that either way he doesn't want to be lumped with them. He fidgets on the seat as the car smoothly goes into motion. Happy didn't raise the partition - he never does when it's Peter and him and they've even started talking a bit, but now Peter wishes he would.

"Not that I'm not excited to see you, Mr. Stark," says Peter with feeling. Excited is an understatement. "But is there something going on?"

Tony throws him an amused look.

"Besides that shopping trip I owe you? Nothing much. Happy's had a new physical, his cholesterol levels lowered from catastrophic to concerning, so there's reason to celebrate."

He realizes perfectly fine Peter means Avengers business, but Mr. Stark can prevaricate with the best of them.

"You paid my favorite burger joint to stop serving me," says Happy unhappily.

"See, I'm really earning that "world's best boss" mug you're about to give me any birthday now. How do you feel about cheeseburgers, Pete? Or maybe we could go for tzatziki? I've no idea what that is but it sounds healthy. What do you say, kid?"

Peter's just about wrapped his head around the fact Mr. Stark's taking him shopping when it turns out they're going for a bite too afterwards so really all he can do is make affirmative noises and hope he doesn't look as lovestruck as he feels.

"Friday found a decent tailor that caters to younger men, on the off chance you didn't want to look as ancient as me," Mr. Stark changes topics in his usual abrupt way. "I know I said shopping but your first suit can't be off the rack."

Peter blinks at this new and unexpected hurdle. The thing is, he's a boy. He still thinks of himself as a boy, and Mr. Stark acts like he thinks the same, even if the shift in touches tells a different story. So he naturally assumed Peter would want a suit. He imagines himself in a three-piece suit like Mr. Stark, and besides Peter's iron conviction that he could never have pulled that off half as well as Mr. Stark, not in a million years, he feels pleased at the prospect. The idea of resembling Mr. Stark in any way could never not please Peter, really. But all the same the suit idea startles him.

The whole point of buying Peter clothes, Peter supposes, is to make Peter look like he belongs. Otherwise he could have just shown up in his regular clothes. For all he knows a teenage girl in a three-piece suit could very well belong at one of Mr. Stark's parties - _especially if it is one of those tear-away stripper suits_ , chimes in a totally not jealous part of Peter's mind - but Peter wouldn't feel like he belongs. Some nondescript unisex clothes would have been fine with Peter, although not particularly exciting.

He opens his mouth to fill the too long silence somehow before Mr. Stark thinks Peter ungrateful and what comes out is: "Actually, I was hoping I could try a- a dress?"

As soon as he says that he realizes how true it is. Peter does like the kind of clothes he wore before, and it's not like he wants to go full Gothic Lolita or anything. But like, he's allowed to wear girls' clothes now. He was technically allowed to do that before too, but Peter's never really liked attention, so the tradeoff never seemed worth it.

It wasn't the plan to blurt it out to Mr. Stark like this though.

When Peter chances a look at Mr. Stark he sees his usual friendly, slightly aloof expression.

"Sure," he agrees without skipping a beat. "A dress it is. Friday, if you would."

"On it, boss," says Friday.

"I'm pretty sure that tz thing is just yoghurt," says Happy, after a beat, in a voice trying so hard to sound normal Peter can basically see sweat drops beading on it. Peter appreciates the effort anyway.

"Then we'll leave it for the next time an alien horde attacks, wouldn't want to be too adventurous with guts all over our nice clean Avengers gear," Mr. Stark says breezily. "Pete, what's the one meal you love that May cooks worse than anything else?"

"Spaghetti," says Peter quickly. He continues guiltily. "Although they're not bad per se, but-"

"I get it," interrupts Mr. Stark. "A woman as lovely as your aunt needs a single flaw, although, boy, is it a big flaw in May's case."

Peter doesn't want Mr. Stark to start waxing poetic about May _again_ and at the same time feels extremely grateful about Mr. Stark not making a big deal out of the dress thing, so he doesn't comment and just wriggles closer to Mr. Stark on the seat under the guise of getting comfortable. Mr. Stark doesn't stretch his arm behind Peter as Peter half-hoped he would but he doesn't move away either, and Peter feels warm and satisfied sitting half on Mr. Stark's discarded jacket, his arm nearly touching Mr. Stark's sleeve.

Nearly satisfied.

* * *

Either the choice for female bespoke tailoring isn't as wide in the city or Friday isn't as picky as Mr. Stark, because they end up going to an ordinary boutique. Well, an ordinary boutique for filthy rich hipsters, in Peter's non-expert opinion.

There Mr. Stark practically throws Peter into the hands of three ecstatic shop assistants who seem far more interested in servicing Mr. Stark than Peter. Mr. Stark basically declares he doesn't give a shit what Peter picks as long as he does it quickly. The last Peter sees of him he's taking out his phone while a fourth woman - this one with a tongue ring, Peter notices miserably - smilingly offers him refreshment, foot massages, her number and who knows what else.

Left on his own, Peter answers questions about the occasion as best he can, doesn't answer questions about his preference because nobody asks him, and gets shown into a dressing cubicle with half a dozen outfits already hanging on the walls where he finally gets to breathe. He strips to his underwear slowly, and finally can't avoid looking at his body. The girl in the mirror is short, thin, with tiny breasts that are all nipple and probably don't require even the sports bras Peter's been wearing. He still has the female equivalent of the lean muscles the spider-bite gave him, only now his shoulders are much narrower and instead his hipbones flare below his narrow waistline. His eyes look bigger somehow on a face that seems as unfortunately plain to Peter's eyes as it always did.

"A great catch you are, Parker," he mutters to himself quietly before shaking off the disappointment and getting on with business. If he grabs something off this first batch Mr. Stark might be persuaded to hang out for longer.

Problem is, Peter hates everything he tries on. It's not the outfits, they look okay on the hangers. On Peter, however, they somehow gain ten levels in ridiculousness. They would probably fit right in at Mr. Stark's party on some model or socialite's daughter, but on Peter they look like tutus on Shetland ponies (only not because that at least sounds cute).

"Do you need any help?" asks one of the assistants on the other side of the partition.

"You mean besides a fairy godmother to turn me back into a pumpkin?" mutters Peter, because he's always resorted to sarcasm when out of his depth.

"What are you going for then?" asks the girl more quietly and somehow more like she sees Peter as a human and not as a shortcut into Tony Stark's good graces.

"I just want to look okay and not like I'm playing dress-up or like I'm-" he thought about Ms. Potts and her razor-sharp, probably cutting-edge fashion business suits. "-like I'm competing with anyone."

There's a beat of calculating silence on the other side of the door before the assistant says, "I'll be one second."

She comes back with only a couple of items but the look of them is decidedly different. Peter puts them on and gives himself an incredulous once over. It's a very decent-looking outfit, high-necked, with a hem that reaches just above Peter's knee, but it looks neither childish nor overly conservative. The red pleated skirt makes Peter's narrow waist and modest hips stand out, and the champagne sweater actually makes his skin not look like grayish oatmeal.

"Can I come in?" asks the girl and Peter calls out a yes while still staring at himself in the mirror.

The shop assistant turns out to be Peter's height. She's carrying a pair of shoes with medium-height, solid looking heels Peter thinks he might be able to walk in. She gives his reflection a look as well and says, "It would look even better without a bra. And if you do strike big and need some more advice or even a personal shopper, I can make you look good enough to leave the competition in the dust."

Peter can't really say anything to that. He tries the shoes on too and tells the assistant he'll take everything. He puts on his own safe, _boy's_ school uniform from his very understanding school that allows girls to wear trousers and probably would allow boys to wear skirts because money bought you tolerance as sure as it did anything else needed for a comfortable life. He very carefully doesn't think about what striking it big might mean, or about how the heels make him look taller, but conveniently not as tall as Mr. Stark.

Once dressed and out of the changing room, Peter finds his own way back to Mr. Stark, the staff obviously not as interested in him now that they got their hands on Mr. Stark's credit card. Mr. Stark looks bored and remote. He glances at Peter briefly through the inscrutable lenses of his aviators and his face shifts, becomes animated in some subtle way before he gestures for Peter to walk ahead. They leave Happy to sort out Peter's purchases and carry the bags.

"Mr. Stark, thank-" Peter starts as soon as they are outside, alone for the first time that day.

Mr. Stark waves Peter off. "None of that, kid. You're doing _me_ a favor, remember. Are you up for something more fun now?"

Peter nods as vigorously as a dashboard bobblehead. He had fun in the car and he was about to have fun now again that the part of the outing he didn't know how to feel about was over.

The right corner of Mr. Stark's mouth lifts up in a sly, asymmetrical grin like he knows just what Peter's thinking. Peter's eyes get pulled in to that mocking half-grin and he realizes he has to say something very soon, create a distraction before Mr. Stark figures him out because if Mr. Stark figures him out he'll put an end to everything, the whole fragile web of ever multiplying intimacies that Peter can have only as long as Mr. Stark doesn't notice it. Or notice how much Peter likes it.

A camera flashes across the road and all traces of a smile disappear from Mr. Stark's face.

"Let's get in the car," he says, and Peter lets Mr. Stark open the door for him and usher him into the back seat, radiating relief.

**Author's Note:**

> If you want a continuation, comment. Helps me stay motivated.


End file.
